Method of and apparatus for the descaling of metals



June 24, 1969. l z. uNTERscHul-:Tz ET AL 3,451,849

METHOD OI" AND APPARATUS `FOR THE DESCLING OF' METALS Filedsept. e. 1964 Sheet of 5 1.\='VE1\/T0Rs: F Zdzislaw Unferschuefz Eusachy Naruszewacz v Tadeusz Kaus .oss garlttorney June 24, 1969 lz,A umERsHUETz `ET Al- 3,451,849

METHOD v0F AND APPARATUS FOR THE DESCALTNG OF METALS Filed sept. 9, 1964 y sheet 2 of 5f l@ a x48 Zdzislaw Unferschuefz Eusachy Naruszewicz Tadeu Kaus INVENTORS.

Attorney Jimerzv. 1969 z; LnsxTERscn-iMETZ ET AlvMETHOD OF AND APPARATUS FOR THEZDESCALING OF METALS Filed sept'. 9. `1964 l F/G. l/

` sheet cfs usfachy Naruszswicz Tadeusz Kaus JNVENTORS.

Y5, A I y F Zgzislaw Unerschugfz vvFiled sept. '9, 1964 June 24,v 1969 l f z.- uNTERscHuETz ET AL `3,451,849

y METHOD OF AND APPARATUS vFR THE DESCLNG OF{METALS sheet 4 @f5 F I I Zdzislaw Unerschusfz Eusfachy Naruszewcz Tadeusz Kaus INVENTORS.

` Attorney June 24, 1969 v Z UNTERSCHUETZ ET AL 3,451,849

METHOD OF AND APPARATUS FOR THE DESCALING OF METALS mit O OO C) sr* O mg t 0 o LD C s l. :e O i O Q 'u O C LL a o O 0 1 O O 2 l: 'u n o t 2 0 U c U* E U Q L *2/ .3 Zdzislaw Unferschuefz -a Eusachy Naruszewicz p Tadeusz Kaus INVENTORS.

BY g qu Attorney United States Patent O 3,451,849 METHOD OF AND APPARATUS FOR THE DESCALING OF METALS Zdzislaw Unterschuetz, Walecznych st. nr. 17/19; and

Eustachy Naruszewicz. Zywiecka st. nr. 7/7, both of Gdansk, Poland; and Tadeusz Kaus, Wladyslawa Lokietka st. nr. 30, Sopot, Poland Filed Sept. 9, 1964, Ser. No. 395,239 Int. Cl. C23g `/00; B23d 79/00; BflSb 1/02 U.S. Cl. 134-1 19 Claims ABSTRACT OF THE DISCLOSURE A method of and a system for descaling metallic surfaces wherein a multiplicity of impact elements are slung against a metallic surface while an electric pulse is applied between the workpiece and the impact elements on contact of the latter with the surface; the impact element or the workpiece is set in vibratory motion transverse to the surface while a weak-base solution may be supplied to increase the rate of descaling.

The present invention relates to an improved method for cleaning the surfaces of metals by removing scale and other impurities, as well as to an apparatus for putting this method into effect.

The main object of the invention is to provide an improved method for cleaning the surfaces or sheets of steel profiles, especially of billets, by the complex application of variable local mechanical forces, electrical arcs and chemical means.

For the removal of scale, oxides and other impurities from the surfaces of metals, various methods have been used heretofore.

There are known, for example, mechanical methods for cleaning the surfaces of metals by hammering, scraping and cleaning (i.e. with brushes). These methods are realized both by hand and by the use of various mechanical devices.

Hand methods are very laborious, hence of low e`1- ciency, and expensive. Mechanical methods also do not assure satisfactory results. Above all they cause rather considerable loss of material andl require Vgreat energy input. Beyond this, the cleaned surface is not quite smooth Ain case of the two first methods, while according to the third lmethod it may be excessively polished.

There are also known methods for cleaning surfaces, especially of sheets, by means of shot peening, sand blasting or etching. These methods also proceed very slowly, require a great work input-often hand work-and the results poor, especially when the impurities' are substantial.

Chemical methods give good results. Their drawback consists in the necessity of using large devices, long process time, and the impossibility of using them when the impurities occur nonuniformly. It is obvious that in practice chemical processes cannot be used `for cleaning large surfaces of sheet products such as the hulls of ships.

There have also been proposed methods for cleaning metal surfaces jointly by` means of brushes and by the action of an electric arc. This known method didnot find widespread application because of the fact that in the arc or in its proximity the service life of brushes is very short.

Other known methods provide for removing the impurities froml metal surfaces by means of brushes and chemical means, which are of use in removing from metal surfaces slight impurities uniformly located.

It has been found that it is possible to carry out the method for complex cleaning metal surfaces, especially sheet surfaces or surfaces of steel profiles such as billets, by utilizing simultaneously the effects of mechanical 3,451,849 Patented June 24, 1969 action, the effects of thermal action (i.e. by making use of the quick local changes of temperatures caused by an electric arc), the thermodynamic effects of local violent pressure changes, and the chemical effects.

The described principles are realized in the method according to the invention with additional utilization of the influence of mechanical resonance of working elements of the mechanical part of the apparatus.

Trials and experiments have shown that an unexpected increase of the action of surface-striking elements occurs at certain frequencies which are determined `by physical and mechanical properties of the vibrating masses. These resonance frequencies depend also-to a less degree-- on the elastic properties of the surface and on the mass of the drops of the used fluid.

As a result of experimental work it has also been found that essential and unexpectedly increased effects are obtained by a proper choice of voltage and electric current for the production of periodically induced and extinguished local electric arcs. It has been found that, after the choice of power parameters i.e. of proper voltage and current, of importance is also the frequency of the current, said frequency corresponding to the optimum frequency of the mechanical vibrations. Omitting theoretical deliberations on the phenomena it must be stated that there exists an interdependence between the percussive pressure, caused by the striking and by the pressure exercised by the mechanical working element against the surface of the sheet, the variations of the resistance of the pressed layer of impurities, especially of metal oxide, the increase of the current front, and the changes of the temperature. Into consideration must also be taken the fact that the fissures, openings and scratches of the layer of impurities allow penetration of the fluid chemical medium which, as a result of rapid temperature and pressure changes increase the separation of impurity layers from the metal and from one another.

In some cases the cleaning of metal surfaces, especially from scales and oxides, proved very advantageous when slight transverse vibrations in relation to forward movement are additionally caused. These `vibrations of small amplitude but of a rather considerable frequency are obtained by the use of vibrators. A small energetic input for causing vibrations gives the same effects as those produced by a very great input of mechanical energy for driving the working elements or of electric energy. When using additional vibration the cleaning effects are sometimes even greater than it is possible to obtain by increasing the mechanical energy, the electric energy or by using more powerful chemical means.

For instance, the acceleration occurring in vibrational modes may be of the order of 30() G i.e. an acceleration greater than that occurring in rocket motors, while the acceleration of the impact strokes are of the order of 10-15 G only. `Of course, the effects are correspondingly increased when vibrations with adjusted frequency are additionally used.

It has been proved that in concrete conditions there are rather distinct optima for the individual components of the method parameters, especially amplitudes.

The apparatus for putting into effect the method according to the invention for cleaning metal surfaces from scales and other impurities is schematically shown in the accompanying drawing, in which:

`FIGURE 1 is a front view of the mechanical part of a stationary apparatus according to the invention for bilateral cleaning of a plate.

FIG. 2 is a front view of the mechanical part of a modification of the apparatus for unilateral cleaning of a slab.

FIG. 3 is a front view of the mechanical part of another modification of the apparatus designed for simultaneously cleaning four surfaces of a body of square profile or section.

FIG. 4 is still another modification of the apparatus designed for cleaning large surfaces which need not be planar or horizontal.

FIG. 5 is a plan view of mechanical working elements according to the invention.

FIG. l6y is a partial perspective view of a roller and of the working element.

FIG. 7 is a side view of an apparatus set in motion along a `surface to be cleaned and simultaneously vibrating transversely to the translatory motion.

FIG. 8 is a side view of the apparatus and of a metal piece to be cleaned, the latter being shifted in the apparatus and subjected to vibrating movement transversely to the translatory motion.

FIG. 9 is an electric feeding circuit with a regulator.

FIG. l0 is an electric circuit with a transformer and a regulator.

FIG. 11 is an electric system with a current source of controllable frequency.

FIG. 12 is an electric three-phase system with a Iblocking transformer.

FIG. 13 shows diagrams of sinusoidally variable voltage and a corresponding diagram of the current adsorbed by elements of the apparatus during the work.

FIG. 14 illustrates the metal and the surface of scales being removed as well as corresponding diagrams of temperature changes which have been produced by the action of the working element of the apparatus.

FIG. 15 illustrates the metal and the surface of the scale as well as curves showing the changes of the value of the coefficient of thermal expansion at temperature changes caused by the action of the working element of the apparatus.

FIG. 16 is a diagrammatic perspective view of an apparatus for carrying out the present invention, some of the parts being shown only in schematic form.

The apparatus for cleaning metal surfaces from impurities by the method according to the invention is composed of the mechanical part, the electric part and of the hydraulic system.

The mechanical part is constituted by the auxiliary elements designed for driving the metal piece to be cleaned-in apparatus of the sationary type-or by elements designed for driving the cleaning device itself along the surface to be cleanedin apparatus of the transportable type. Furthermore, the mechanical part yis constituted 'by the elements designed for driving the working element, and by elements producing the transverse vibrations.

The electrical part is formed by the systems for controlling the electric parameters and by the Working elementsin common for the electrical part and for the mechanical part. The control systems are constituted by known voltage regulators, current regulators and frequency changers.

Furthermore, elements of the electrical part are the systems designed for energizing the drives of the advance, of the working elements and of the vibrators, and the systems associated with them and designed for regulation, control, automatization and safe-guard.

The hydraulic part is formed by the system designed for the supply of chemical means to the working regions of the working element, the end of said system being provided with spray or atomizing nozzles.

Referring to the accompanying drawing, an apparatus of stationary type for cleaning bilateral surfaces of the metal plate (FIG. 1), is provided with two lsets of cleaning elements 16 and 17, preferably horizontally superposed. The metal element 18 to be cleaned is introduced horizontally between both the sets of cleaning elements 16 and 17. The sets 16 and 17 are secured in elastic dampers 19 in the housing 20.

In a similar manner is designed the modification of the apparatus (FIG. 2) for unilaterally cleaning the surfaces of metals. The set of cleaning elements 21 is preferably placed horizontally and above the element 22 to be cleaned. The set 21 is suspended resiliently to the housing 24 by means of dampers 23.

Another modification of the apparatus (FIG. 3) designed for quadrilaterally cleaning the surfaces of a metal body, e.g. of billets 25 of steel, is provided with four cleaning sets 26 which are resiliently secured in the housing 28 at an angle of 45 by means of dampers 27.

Still another modification of the apparatus (FIG. 4) designed for unilaterally cleaning large surfaces of metals, not necessarily planes and not necessarily horizontal, e.g. the hulls of ships, is provided with one cleaning set 29, which is secured in a resilient manner by means of dampers 31 to the frame 34. The surface 30 to be cleaned is simultaneously the track for the car 32 which is provided with a suitable guide 33 secured to the frame 34.

The cleaning sets 16, 21, 26 comprise working elements (FIGS. 5 and 6) in form of annular impact elements 36, e.g. pipe sections (cylinders) or rings. The annular impact elements 36 are loosely mounted on rollers 35. It is essential that the inner diameter of the annular impact element or annular 36 be greater than the diameter of the roller 35 by the sector 38 (FIG. 8). It is of great importance that the individual annuluses 36, which are mounted on neighboring rollers 35 be parallel to one another, overlap each other by the dimension 37 and are placed (i.e. are interleaved). The individual parallel rollers 35 may be secured to circular lateral disks or by groups in segments of the crawler chain type.

The kinematic solution of the drive of the translatory motion and of the vibrating movement may be either in the form of imparting both the movements to the cleaning set 39 (FIG. 7) moving in a translatory motion with the direction 44 and in a vibrating motion in the directions 43 and 45 which are perpendicular to the direction 44 of the translatory motion of the elements 36, along the surface 40 being cleaned, or the cleaning set 41 remains at rest (FIG. 8) while the translatory motion with the direction 47 as well as the vibrating motion having the directions 46, 48 are imparted to the material 42 to be cleaned. The simplest realization of the electric sys- 0 tem (FIG. 9) consists in supplying the electric energy from the line network 49, adjusting the parameters in the regulator 50 (i.e. frequency, voltage, current) with phaseshift, and applying the current to the working set 51 and to the metal body 52 being cleaned. This realization is best when a part of parameters is conveniently adjusted already in the supply network, hence in great cleaning works equipped with a series of devices.

Generally it is necessary to lower preliminarily the voltage and then to perform the regulation. Such a system (FIG. 10) connected to the network 53 is provided with a controllable blocking transformer 54 and only then a regulator 55 from the output of which the voltage is led to the working set 56 and to the metal body 57 to be cleaned.

Small cleaning devices, especially transportable ones, may be fed from the plant network (FIG. l1). From the network 58 the voltage is led through the controllable frequency changer 59 to the working set 60 and to the metal 61 which is being cleaned.

Great cleaning devices, especially bilaterally operating ones, are fed from the three-phase alternating current network (FIG. 12). From the net 62 the voltage is led through the controllable blocking transformer 63 and the controllable frequency changer to both the sets of working elements 65, 66 and to the metal 67 which is being cleaned.

The curves (FIG. 13) of the sinusoidally variable voltage U and of the current I illustrate the occurring electric phenomena. On reaching a defined value of the Voltage 68 numerous current pulses 69 appear. The curve of the current run J shows the summarized current absobed by the cleaning device. The currents flowing through the individual working devices are of the stroke-pulse-type.

The curves (FIG. 14) illustrate schematically the course of removing the layers of impurities from the metal. There remain fissures 72, and the impurity layer 76 crumbles to pieces 73 and 75. Some fissures 74 are accompanied by a process of curving the pieces 73, 75. The schematically shown distribution of occurring temperature changes in the impurity layer 70 and in the metal 71 is caused by the different thermic properties i.e. by the conductance, the specific heat, the thermal storage capacity etc. of both the phases (i.e. the impurity phase and the metal phase).

The inter-layer stresses (FIG. 15) i.e. the forces 82, are also caused by the different values of the expansion coefficient and the expansion changes-curves 80 and 81 of the impurity layer 83 and of the metal 84.

The process of cleaning metal surfaces to remove irnpurities according to the present invention proceeds as follows. The contaminated metal surface is subjected to a mechanical, thermic and chemical complex action.

The layer of impurities and the neighbouring metal layer are subjected to the action of local periodically variable mechanical pressures. The pulses are of the character of mechanical strokes. They are obtained by periodical strokes executed by metallic working elements, which are slung forcefully against the surface, loosely mounted on rollers.

At the same time great heat portions are directed very quickly on a particular point. For this purpose shortlasting pulses of strong currents are caused to flow through the spots being subjected to pulses of mechanical pressure.

The rapid pressure increase caused by the strokes i.e. the change of kinetic energy into potential energy of the pressed layer and into thermal energy, causes a rapid local temperature increase so that sometimes additional supply of current may be unnecessary.

The acute striking front of the current pulse is caused by the quick and good contact of the metal working elements with the surface to be cleaned, with proper phase relation of current and voltage. An advantageous decrease of the resistance of the impurity layer caused by pressure, also takes place. Finally, the effects are increased due to the use of fluid chemical means.

A similar acute clip of the current pulse is obtained as a result of a quick resilient recoil of the working element and of arc-break. The used chemical means and the arising gas phases produce a local extinguishing of electric arcs.

The increase and decrease of the current and consequently also of the temperature produces considerable forces opening the impurity layer, crumbling the impurities and removing them from the pure metal. These forces depend on the difference expansion coefficients of the metal and of the impurities.

Mechanical strokes are of course very useful in removing the loosened and crumbled pieces of impurities.

A considerable increase of mechanical effects is obtained by choosing the frequency of periodic pulses so that it is a resonance frequency.

Such an unexpected increase of the effects is obtained by choosing the frequency of periodic current pulses according to the frequency of the alternating current feeding the apparatus.

A manifold increase of the descaling effect is obtained if, in addition to the mechanical means, vibrations having a direction transversal to the advance motion and to the metal are used. And here is also chosen such a resonance frequency of the vibration so as to be equal to one of the harmonics of the basic resonance frequency of mechanical vibrations, having regard to known deviations caused by damping and coupling effects.

The chemical action is realized by supplying fluid chemical means, especially weak base solutions, to spots intended to be subjected to complex cleaning prior to the mechanical process and the thermal process.

Beyond the insignificant known action of solutions, which however appears in perceptive effects after a long time and in relatively well known concentrations, the essential improvement resulting from the additional use of this action, consists in distinct facilitation of the flow of the striking current wave, vigorous extinguishing of the arc and the most important thermodynamic action.

The fluid penetrating into the fissures, openings and scratches of the impurity layer is rapidly heated together with this layer. The heated layer in the first moment extends and closes the openings, fissures and scratches. The fluid contained therein is rapidly heated and turns into vapor of immense pressure. The pressure of the vapor contributes remarkably to the destruction of the impurity layer.

T hese effects occur also in heating caused by the mechanical action and in some cases the use of electric action is unnecessary.

It has been found that the fluid, preferably a weak alkaline solution of KOH or NaOH, may be supplied in atomized form. The effects are the same as in supplying a liquid compound, and in some cases it is more advantageous to carry out the process in a half-dry way.

The surface of the cleaned metal is relatively smooth but not too much, and it reveals a great adherence to coatings, especially to paints.

The chemical process prior to painting is of special advantage because it is possible-using known suitable additions-to remove impurities detrimental to covers.

What we claim is:

1. A method of cleaning the surface of a metallic body comprising the steps of repeatedly slinging individual impact elements against the surface of said metallic body; applying across said impact element and said metallic body an electrical pulse adapted to heat said surface of said metallic body upon contact of said elements therewith; and imparting to at least said metallic body or said elements a vibratory movement in a direction transverse to said surface simultaneously with the slinging of said elements against said surface and the passage of electric current through said elements and said metallic body.

2. The method defined in claim 1, further comprising the step of applying to said surface a chemical-cleaning solution capable of penetrating surface impurities concurrently with the slinging of said elements against said surface.

3. The method defined in claim 2 wherein said metallic body or said elements are vibrated at a frequency related to the frequency of the electrical pulses applied to said surface.

4. The method defined in claim 3 wherein said metallic body or said elements have a natural frequency of vibration corresponding to the frequency of said vibrations.

5. The method defined in claim 1, further comprising the step of vibrating said metallic body or said elements relative to the other in a direction perpendicular to the first-mentioned direction of vibration.

6. An apparatus for the descaling and cleaning of a surface of a metallic body comprising a set of impact elements engageable individually with said surface of said body; means for slinging said impact elements repeatedly against said surface; circuit means connected between said impact elements and said body for passing electric current pulses through said surface upon engagement of said elements therewith; and means for relatively vibrating said body and said set of elements in a direction transverse to said surface.

7. The apparatus defined in claim 6, further comprising nozzle means for directing a chemical-cleaning liquid onto said surface in the region of contact of said elements with said surface.

8. The apparatus defined in claim 7 wherein said elements are annular members and the means for slinging 7 said members against said surface includes a respective shaft passing with clearance through each member and drive means for displacing said shaft relatively to said body.

9. The apparatus defined in claim 8 wherein at least two sets of said impact elements are provided and engage opposite sides of said body, said -body being set between the sets of impact elements.

10. The apparatus as defined in claim 6 wherein the last-mentioned means includes resilient suspension means supporting said set of elements with freedom of vibratile motion.

11. The apparatus defined in claim 6 wherein said set of elements is disposed horizontally and above said workpiece.

12. The apparatus defined in claim 6, further comprising means for relatively displacing said body and said set of elements to sweep said set of elements across said surface.

13. The apparatus defined in claim 12 wherein the last-mentioned means includes a carriage supporting said set of elements and shiftable on said body.

14. The apparatus defined in claim 6 wherein the lastmentioned means includes a vibrator connected with said set.

15. The apparatus defined in claim 6 wherein the lastmentioned means is a vibrator connected with said body.

16. The apparatus defined in claim 6 wherein said circuit means is connectable with an electric network and includes a controllable frequency changer.

17. The apparatus defined in claim 6 wherein said circuit means is connected to an electrical network and includes a blocking transformer between said network and said set of impact elements.

18. The apparatus defined in claim 6 wherein said circuit means includes control means for varying at least one of the following parameters:

(a) the electric power delivered to said set of impact elements and said body; (b) the voltage applied across said impact elements and said body; (c) the current passed through said impact elements and said body; and (d) the phase shift of the electrical energy supplied to said set and said body. 19. The apparatus dened in claim 6, further comprising means for controlling the frequency of the relative vibration of said elements and said body.

References Cited UNITED STATES PATENTS 635,938 10/1899 Mason. 1,984,762 12/1934 Roberts. 1,998,851 5/1935 Shields. 2,133,231 10/1938 Schermer 134-15 2,134,457 10/1938 TaintOn 134-1 X 2,465,297 3/1949 Thompson et al. 134-15 X 2,562,899 8/1951 Finn. 2,650,888 9/1953 Pottberg 134-15 2,717,845 9/1955 Carter 134-15 X 2,735,232 2/1956 Simjian. 2,883,310 4/1959 McAuley et al. 131--1 3,174,491 3/ 1965 Faler.

FOREIGN PATENTS 926,094 5/ 1963 Great Britain.

TIM R. MILES, Primary Examiner.

U.S. Cl. X.R. 

